It was a perfect storm for dissatisfied patients and burnt-out clinicians, says Thomas Bodenheimer, a doctor and professor at the University of California, San Francisco’s School of Medicine. While specialists could often combat falling fees by doing more procedures, primary-care doctors get paid by the office visit, so all they could do was cram more appointments into a day and increase their panel size—the number of patients in their practices. For primary-care doctors to do a good job, says Bodenheimer, panels should be below 1,800. Today the average primary-care doctor in the U.S. is responsible for about 2,300 patients. At so-called Medicaid mills—clinics that see mostly poor patients covered by state Medicaid plans—panel sizes can reach 3,000 per doctor.

Today visits are still short, while treatment regimens for common conditions like diabetes and heart disease are more complicated. The number of required tests and conditions primary-care doctors are supposed to screen for has skyrocketed. It’s estimated that a doctor with a panel of just 2,000 patients—and without a strong primary-care team—would have to spend more than 17 hours a day providing all of the recommended care. “When you have only 15 minutes per patient, then there are home visits and hospital visits, you feel like you’re on a hamster wheel,” says Bodenheimer. “I was a full-time primary-care doctor for more than 30 years. It almost killed me.”